Big cam Small Block Gs1100?

[gs1150streetracer]

Hi GSR
Im still fixing the "8k broken cam chain bike"almost done....was thinking about going with a bigger cam set up for more power,I have a set of G3 cams now, I know a set of G4s can fit anything bigger with a stock 1150 head?,what the largest set of cams or Combo you can run with a small block GS..1166 1229 or 1260?I seem to have all 3 at this point..The engine I have in mind is a 1166,the bike will be dragstrip only and I have a 24v onboard super squirel starter...Any input would be great.....

 

[rapidray]

How much compression & headwork, Rick? What size valves & how much RPM are you wanting to spin the thing. Rather than an 1166 I would go a 1229 as more ccs are always a good thing! Call me if you want to discuss. Ray.

 

[blowerbike]

bigger cams does not always mean more HP grasshoppa.

 

[trippivot]

Cam lift should match the flow characteristic of your head. nothing else really matters.

if the head increases flow until .380 and levels off, get a cam that lifts the valve only that much. ( rocker ratio considered)

I mean if the head stops flow at .350 there is no reason to lift the valve any higher. PERIOD

 

[posplayr]

Cam lift should match the flow characteristic of your head. nothing else really matters.

if the head increases flow until .380 and levels off, get a cam that lifts the valve only that much. ( rocker ratio considered)

I mean if the head stops flow at .350 there is no reason to lift the valve any higher. PERIOD

Not sure I understand your meaning. When I saw the comment I went to look at the flow numbers on my head (Terry at headsbikesmopars did for me)and how it matched the 0.340 cams I'm running. I could have gone 0.348 which according to Ray generates bunch more power. According to the the graph by the time you get to 0.275 to 0.300 there is no more flow increase with lift.

Looking at the flow rate plot attached to this post, you would think increasing from 0.340 to 0.348 would make no diff. There must be more to it than just flow rate right?

http://www.thegsresources.com/_forum/showpost.php?p=999223&postcount=29

P.S. I think I'm taking your statements too litterallly

 

[trippivot]

head is where the magic is.

head is where the magic is.

those were just generic numbers I used.

All I am saying cam lift has to match headflow nothing else.

One of my heads flow 126cfm at .450 lift 10" test on intake side.

who cares about exhaust as long as it is 60% of the intake flow. there is no increase in power (turbo is the exception) on increasing the exhaust over that int/exh percentage.

now speaking at my engine 31mm/26mm G13(.420)G7(.380)
the flow slows after .400 but keeps increasing until .450
This is where time becomes a consideration for my specific engine design... and wasting time for 3cfm from .420 to .450 is not efficient enough for me so I decide to cut it off there. and less lift means your valve springs will last longer.

he can design his engine any way he likes but thinking cam lift is related to cylinder displacement -only- needs to be corrected.

cause it is better to match flow and lift - then it dont matter what displacement engine you put the head on -- it's going to kick ass and produce it's highest potential as a well balanced head should.

over headding is as bad as over carbing

over headding == no power, sluggish torque no port velocity

over carb ==no bottom end, bad idle excellent hi-rev power

the opposite is also true and better most of the time

small carbs=big engine= great bottom end great low end throttle response. top end power restricted by total flow

small head = big engine = massive bottom end torque, great low end power falls off drasticly on top. top end restricted by total flow

get the head matched to itself and then dial it in with LC numbers to reach the highest potential as per displacement combination will allow.

 

[posplayr]

those were just generic numbers I used.

All I am saying cam lift has to match headflow nothing else.

One of my heads flow 126cfm at .450 lift 10" test on intake side.

who cares about exhaust as long as it is 60% of the intake flow. there is no increase in power (turbo is the exception) on increasing the exhaust over that int/exh percentage.

now speaking at my engine 31mm/26mm G13(.420)G7(.380)
the flow slows after .400 but keeps increasing until .450
This is where time becomes a consideration for my specific engine design... and wasting time for 3cfm from .420 to .450 is not efficient enough for me so I decide to cut it off there. and less lift means your valve springs will last longer.

he can design his engine any way he likes but thinking cam lift is related to cylinder displacement -only- needs to be corrected.

cause it is better to match flow and lift - then it dont matter what displacement engine you put the head on -- it's going to kick ass and produce it's highest potential as a well balanced head should.

over headding is as bad as over carbing

over headding == no power, sluggish torque no port velocity

over carb ==no bottom end, bad idle excellent hi-rev power

the opposite is also true and better most of the time

small carbs=big engine= great bottom end great low end throttle response. top end power restricted by total flow

small head = big engine = massive bottom end torque, great low end power falls off drasticly on top. top end restricted by total flow

get the head matched to itself and then dial it in with LC numbers to reach the highest potential as per displacement combination will allow.

OK Thanks, I understand balance is best.

 

[trippivot]

I hope the jibberish makes some sense.

I hope the jibberish makes some sense.

big cams are cool !!

but if the port quits flowing at X (X=what ever lift C.F.M. maxes out at)
why would you want to lift the valve more than X ?

I'm sure we all drool over big 'ol bump sticks!! I do.

but too big and you are going to go slower than stock and wearing out valve springs and then comes valve float and next valve to piston contact.

bada boom. big badda boom

to really know what cam you need==get your head on a flow bench . get the basic graph. buy a similar pair of camshafts - according the intake numbers and the exhaust will be fine.
heck we all have exhaust pipes that scavenge at 130% of what is necessary- Vance and hines megaphone, mac, jardine, star,murray

that way your money is not spent to go slower.

I have a Trustworthy performance shop that I get my scientific head testing done at. head test is less than $50 bucks for 1 port int and exh the owner is multi time national motorcycle bracket racing champion. Builder, racer and good friend to me. He wont answer 40 questions but he will give you accurate information to build a great engine. IDBA IHRA NHRA blah blah blah

 

[posplayr]

big cams are cool !!

but if the port quits flowing at X (X=what ever lift C.F.M. maxes out at)
why would you want to lift the valve more than X ?

I'm sure we all drool over big 'ol bump sticks!! I do.

but too big and you are going to go slower than stock and wearing out valve springs and then comes valve float and next valve to piston contact.

bada boom. big badda boom

to really know what cam you need==get your head on a flow bench . get the basic graph. buy a similar pair of camshafts - according the intake numbers and the exhaust will be fine.
heck we all have exhaust pipes that scavenge at 130% of what is necessary- Vance and hines megaphone, mac, jardine, star,murray

that way your money is not spent to go slower.

I have a Trustworthy performance shop that I get my scientific head testing done at. head test is less than $50 bucks for 1 port int and exh the owner is multi time national motorcycle bracket racing champion. Builder, racer and good friend to me. He wont answer 40 questions but he will give you accurate information to build a great engine. IDBA IHRA NHRA blah blah blah

I dont know much about this other than what I have been told. When I was discussing my head with Terry, I gave him the same concern about having too big of valves and too much flow for a street motor.

He assured me that was not the case and that you should always make the head flow as much as you think you will ever need. Anyway he upped my CFM by about 22-25% with some street porting, back cut valves but did go to 28mm 1150 intake valves.

I don't figure I'm using all that flow and would see plenty of benefit from some 0.348's (not that I need them)

 

[rapidray]

Jeff, you forgot to mention duration & how it affects the engine according to the the static compression. Also, bigger engines will make what seems like a big cam in a smaller cc engine seem anemic! Get your info from whoever you want, I get mine from 30 years of doing it MYSELF & trying just about any combo you could think of. The head is the key to power but there are MANY variables that affect the outcome. Ray.

 

[posplayr]

Jeff, you forgot to mention duration & how it affects the engine according to the the static compression. Also, bigger engines will make what seems like a big cam in a smaller cc engine seem anemic! Get your info from whoever you want, I get mine from 30 years of doing it MYSELF & trying just about any combo you could think of. The head is the key to power but there are MANY variables that affect the outcome. Ray.

Well just thinking about it like an engineer, the total flow when the engine is running is not what you measure on a flow bench (under static lift conditions).

Total flow will be an increasing function of duration and lift (And probably compression) even if the flow bench CFM flattens out at 0.300".

We could probably calculate the average flow using the static CFM data and the cam profile (duration and lift). Of course other factors like carb and exhaust flow rates will come to bear and might be the limiting factor as well.

Ok i'm done :-\\\

 

[madjack57754]

Just a few thoughts on cams. Cam selection can be a can of worms. Lots of variables affect final results. Big carb/cam combinations with mild head porting that nobody would run at sea level have worked great above 6000ft. The whole idea is to get as much oxygen and not just air into the cylinder and keep it there for the cycle. Long duration cams with not a lot of lift tend to work with blowers and turbos because of pressure rather than vacume filling the cylinder. Lots of overlap has worked for me with nitrous on very high rpm motors. Every combination is going to like something different.

 

[trippivot]

yep everyone is making good valid points.

he just wanted to know how big of cams will fit into a stock gs head. I know the G3 and G4 from the catalog description.

but determing the lift is one thing. mechanical limit / obstructions / budget

The duration discussion can happen when we find out HOW he wants his engine to behave. and if he has emissions tests to pass.

 

[blowerbike]

the key word here is "stock" head.
whats a stock head flow and at what lift?

hey,
where's that pro head porter dude that posted in the service area here.
larry cavanagh or something.
i bet he would know right off and then none of us amateurs would have to guess.

 

[rapidray]

A stock GS1100 head flows 83-87 cfm @.350 lift @ 16" on my flowbench. The 1150 head a little more on the intake side. I can get WELL over 100 cfm @ the same lift with GAIN in port velocity still using stock valves. Ray.